Piperidine derivative and process of producing it



Patented Dec. 16, 1930 UNITED STATES SAMUEL I. IuEI-VAIN, OF MADISON, WISCONSIN PIPIEIDDTE DERIVATIVE AND PROCESS 01" PRODUCING Ill.

Ho Drawing.

My invention relates to certain piperidine derivatives, and the process of producing them.

The object of the invention is to produce certain synthetic substances which are effective as local anesthetics. Some of these synthetic substances are ve highly effective as local anesthetics, and at t e same time possess sufiiciently low toxicity and sufliciently low irritating properties to make them safely and conveniently practical for clinical use. The various substances which come under .my generic invention as hereinafter defined vary in these several properties; for

my invention includes quite a large number of compounds.

These compounds are piperidine derivatives in whic the nitrogenqoined hydrogen atom of iperidine has been replaced by a radicle o the general formula (GILL-000R,

3.1 .3. ):!I B (4) (1) (CHg)x-OCOB' in which R is an aromatic radicle and a: is

40 an integer as stated above, 3/ in four of the five places where it a cars is a hydrogen atom, and y in the fif t d lace where it appears is an organic radic e.

The particular y which is an organic radi- Q5 cle may be in any one of the five places where Application fled 1mm 80, 1827. Serial Io. 179,725.

3 appears in the formula. That is, counting the nitrogen atom as the 1 position, the carbon-joined hydro n atom which is replaced by an organic ra icle may be in the 2 position, the 3 position, or the 4 position; it being obvious that the 6 position and the 5 position indicated are in reality the same as the 2 position and the 3 position respectivel The organic radicle at such one y may e of a variety of types, but desirably contains an aliphatic roup of the parafiin series; as for instance iy being a methyl group, an ethyl group, a pro yl group, or a carbethoxy group. It desirab y contains an alkyl group having less than four (4) carbon atoms.

In the above formula, the group (CH does not necessarily indicate strictly the methylene unit taken some integral number of times, but is intended to cover broadly a radicle in which the relation of the total carbon to the total hydrogen is in the proportion indicated. That is, assuming for instance that .2: equals 3, the expression (CH is intended to include not only a bivalent radicle of three methylene groups, but also other bivalent radicles having the same proportion of total hydrogen and total carbon, such as a methyl substituted ethylene group;

Further, while the w in this formula may be any practically possible inte er, I prefer that it be a plural integer less t an six (6), desirably three (1%).

The radicle is an aromatic radicle. Indeed, I prefer that R shall be a phenyl group, either unsubstituted or substituted; such for instance as an amino-substituted phenyl, and with the amino group itself either unsubstituted or mono-alkyl or di-alkyl substituted.

A convenient general process of preparing substances such as shown in the foregoing formula is the followin A halogen-substitute alcohol is caused to react with either one or the other of the following substances: (a) a substituted piperidine; and (b) a benzoylating agent, such for instance as benzoic anh dride, or a benzoyl halide. For the substituted phenyl compounds a convenient benzoylating agent is a nitro benzoyl chloride. The compound obtained as a result of the foregoing reaction is then caused to react with the other of said two substances named above-that is, with either the substituted piperidine or with the benzoylating a cut, according to which one it was that di not take part in the first-named reaction with the halogen substituted alcohol. If the compound resulting from the firstnamed reaction given above is directly available, without being speciall prepared, it can be used as the bases for t e second reaction given above; and my claims are intended to cover the second reaction alone as well as the s uence of the two reactions. If the benzo latmg agent used is a nitro benzoyl chlori e, the result of the second reaction given above should be followed by a third or subsequent step, of reducing the substituted piperidino-a lnitro-benzoate obtained as the result of t e second reaction to a substituted pipzridino-alkyl amino-benzoate.

any case, the result of the second or third reaction is a base, of the general formula given above. In many instances, this base is relatively insoluble in water, or has too low a water-solubilit to be conveniently available clinically. To increase the water-solubility of the substance, it is desirably transformed into a salt, by the combination with it of an acid. Various inorganic acids can be used, such as hydrochloric acid, and various or nic acids, such as lactic acid. If hydroc oric acid is used, the salt formed has the following general formula s -ooon' ci i q l; A

in which a, y, and B have the same significance as before. These salts are quite soluble in water,'and are the desirable form in which the substances are used as anesthetics. However, my invention is intended to cover both the bases and the salts.

In some cases, the desired hydrochloride of the tertiary amine, as first obtained, is contaminated with some of the hydrochloride of the second amine-i. e., with some of the h drochlori e of the unchanged piperidine.

o purify it, an aqueous solution 0 it is treated with an excess of alkali, such as sodium hydroxide. The resultant alkaline suspension of the free base is shaken with benzoyl chlpride, whereby any unchanged secondary amme present is converted to an amide. The aqueous suspension is extracted with ether" as the hydrochloride from the ether solution.

I give below a number of examples of compounds embodying my invention, and their method of preparation. In these, temperatures are given in the centigrade scale.

Example 1 Gamma 2 methyl piperidino) propyl benzoate hy rochloride,

CH;CHCH;

Fifteen g. of Q-methyl piperidine and 15 g. of gamma-chloro-propyl benzoate are mixed, and heated under a reflux at a temperature of 120-140 for -40 minutes. The reaction mixture is then cooled, and treated with 100 c. c. of ether, and the precipitated secondary amine hydrochloride (i. e., some of the hydrochloride of the unchanged piperidine) filtered off. Hydrogen chloride gas is passed into the filtrate, and crude gamma- (2 methyl-piperidino) -propyl benzoate hydrochlorlde thereby precipitated. The ether is decanted from the precipitate, and the latter is dissolved in 20 c. c. of cold water. This solution is treated with 5 c. c. of sodium hydroxide and 5 c. c. of benzoyl chloride, and the resulting mixture shaken vigorously until the odor of the benzoyl chloride has disappeared. In this manner any unchanged secondar amine is converted into an amide.

The al aline solutionwhich contains the free base, gamma-(2-methyl-piperidino)- ,propyl benzoate in suspension-is extracted with ether, and the ether extract is treated with hydrogen chloride; whereupon the gamma- 2-methyl-piperidino) -propyl benzoate hydrochloride 1s precipitated. The product is re-crytstallized from an alcohol-ether mixmm, a er which it melts at 167-9". The yield is about of the theory.

The corresponding beta- 2-methyliperidino) -alpha-methyl-ethyl nzoate ydrochloride and beta(2-methyl-piperidino')- beta-methyl-ethyl benzoate hydrochloride, as well as their free bases, may be prepared in an analogous way to that outlined above for the gamma-(2-methyl-pi 'dino) -propyl. benzoate hydrochloride. the same general method may be used in preparing the analogous h drochlorides, and their free bases, with t e methyl substitution in the 3 and 4 positions of the piperidine nucleus as well as in the 2 position given.

Example 2 I Gamma 2 rop lpiperidino) propyl benzoate hyilrocgilori de,

cincn-cn,cmcm ch. ii on ch26; MOO-O and the desired tertiary amine is precipitated Twelve g. of 2-propyl piperidine (confine) scribed in Example 1 1,1a4,eos

and 10 g. of gamma-chloro-pro yl benzoate are heated together under a refiiix in an oil bath at 14(L160 for 30 minutes. The product of the reaction is gamma-(2-propyl-piperidino)-propyl benzoate and an equivalent amount of coniine h drochloride. The tertiary amine is puri ed and isolated as the hydrochloride in the same way as that defor the Q-methyl derivative. The gamma (2-propyl-piperidino)- propyl benzoate hydrochloride melts at 184186.

Variations similar to those given under Example 1 may be made to produce the analogous 3-propyl-piperidino and the 4-propylpiperidino compounds; and also to produce the various types of alkyl benzoates mentioned under Example 1.

E wample 3 Gamma (3 methyl piperidino) propyl benzoate hydrochloride,

CHa-CH-CH;

I give two methods of preparing this compound:

A. Ten g. of 3-methyl piperidine and 10 g. of gamma-chloro-propyl benzoate are heated together at 100 on a steam bath for 30 minutes. The reaction mixture is cooled, and treated with 100 c. c. of ether. The secondary amine hydrochloride is filtered from the ether solution of the tertiary amine, and the latter is precipitated as the hydrochloride with hydrogen chloride. The precipitated hydroc loride is re-crystallized from an alcohol-ether mixture. The yield is 10 g., and the product melts at 178-180".

B. Gamma (3 methyl piperidino) -propyl benzoate hydrochloride may also be prepared in the following manner: 20 g. of 3- methyl piperidine and 10 g. of trimethylene chlorohydrin are heated together on a steam bath for {10 minutes. The reaction mixture is treated with 100 c. c. of benzene, and the preci itated B-methyl piperidine hydrochloride ltered off. To the filtered benzene solution is added 18 g. of benzoyl chloride, and the resulting solution is refluxed for 4 to 5 hours. The gamma-(3-methyl-piperidino)- propyl benzoate hydrochloride separates from the benzene solution during the refluxing, and more completelyon cooling. It is re-crystallized from an alcohol-ether mixture.

Process A given above is substantially the same process for the 3-methyl-pi eridino compound as is given under Examp e 1 for the 2-methyl piperidino compound; save that, it is not carried through the step of final urification given under Example 1. This 18 because in the preparation of the 3-methylpiperidino compound, the secondary amino does not remain after the initial reaction as it does in the case of the 2methyl-piperidino compound. That is, the reaction in the case of the 3-methyl piperidino compound is more complete than is the case with the 2-methylpiperidino compound under conditions of reaction as described above.

Both of methods A and B under Example- 3 can be used for preparing the .Z-methylpiperidino compounds and the 4-methylpiperidino compounds; save that in preparing the Q-methyl-piperidino compound the step of further purification outlined in Exam le 1 is desirable.

urther, both of processes A and B given under Example 3 ma be used for preparing the various types 0 alkyl benzoates mentioned under Example 1.

Example 4 Beta- (3-methyl-piperidino) ethyl benzoate hydrochloride,

cm-cln (Ian,

on N- CH 0-00 on, n,

Example 5 Gamma- 3-carbethoxy-piperidino) -propyl benzoate hydrochloride,

C:H|0OCC GHQ CIH, gyiz-rcn'ero-co-o This compound is prepared in exactly the same manner as gamma- (3-methyl-piperidino) -propyl benzoate hydrochloride of Example 3, both processes A and B, except that an equivalent amount of 3-carbethoxy piperidine (ethyl nip ecotate) is used instead of the 3-methyl piperidine. It melts at 161-3".

Various isomeric alkyl benzoates analogous to those mentioned under Example 1 may be made in the same general way; and the carbethexy groups may be in either the 2 position or the 4 position as well asin the 3 position.

Emple 6 Gamma- 3-me thyl-piperidino) propyl para-amino- The procedure described in Example 3-3 is followed, except that 22 g. of p-nitrobenzoyla chloride 15 used instead of the 18 g. of nzoyl chloride. The resulting gamma- 3-methyl piperidino) -propyl p nitrobenzoate hydrochloride melts at 190-2". The nitro group of this com and is reduced to an amino group either y iron powder and water with a trace of hydrochloric acid, or by hydrogen and catalytic platinum with alcohol as a solvent. The gamma-(3-methylpi ridino) -propyl p-amino-benzoate hydroch oride melts at 158160.

Isomeric analogues compounds may be made in the same general way; and the methyl group may be in either the 2 position or the 4 position as well as in the 3 position.

E sample 7 The preparation of this compound is exactly the same as that described in Example 6 for gamma-(3-methyl-piperidino)-propyl p-amino-benzoate hydrochloride, except that an equivalent amount of 3-carbcthox vpiperidine is used instead of 3-methyl-piperidine. The meltin point of gamma-(Scarbethoxy-piperidino -propyl -nitro-benzoate hydrochloride is 1779, an of the gamma- (3-carbethoxy-piperidino) -propyl p-aminobenzoate hydrochloride is nil-112.

Isomeric analogues, as before, may be made in the same general way; and the carbethoxy group may be in either the 2 position or the 4 position as well as in the 3 position.

Analogous mono-alkyl-amino and di-alkylamino benzoate hydrochlorides may also be produced. The mono-alkyl and di-alkyl benzoic acids may be esterified with the halogensubstituted alcohols in the usual manner. lhe resulting halogenated esters may then be caused to react with the various substituted piperidines mentioned above.

The examples given above are merely examples of the various compounds and processes included in my invention. They show in general the type of variations which the invention includes, but are not given as limitations on the generic invention.

I claim as m invention: 1. A piperi no derivative including a substance of the general formula in which R is an aromatic radicle, m is an integer, and y in one place is an aliphatic grou and in each of the four other places is a by rogen atom.

2. A piperidine derivative as expressed in claim 1, in which a: is a plural integer.

3. A piperidine derivative as expressed in claim 1, in which a: is a plural integer less than six (6).

4. A piperidine derivative as expressed in claim 1, in which m is three (3).

5. A piperidine derivative as expressed in claim 1, in which R is a phenyl radicle.

6. A piperidine derivative as expressed in claim 1, in which R is an amino-substituted phenyl group.

7. A piperidine derivative as expressed in claim 1, in which the 3 which is an aliphatic group is of the parafiin series.

8. A piperidine derivative as expressed in claim 1, in which the y which is an aliphatic group is an alkyl group.

9. A piperidine derivative as expressed in claim 1, in which the 3/ which is an aliphatic group is an alkyl group having less than four (4) carbon atoms.

10. A piperidine derivative as expressed in claim 1 in which R is an unsubstituted group.

11. A piperidine derivative as expressed in claim 1, in which the y which is an aliphatic grou is an alkyl group and in which R is an unsu stituted phenyl group.

12. A salt of a piperidine derivative of the formula set forth in claim 1, and an acid.

13. A salt of a piperidine derivative of the formula set forth in claim 1, and an inorganic acid.

14. The hydrochloride of a piperidine derivative of the formula set forth in claim 1.

15. The process of producing substituted piperidino alkyl benzoates of the composition set forth in claim 1, which comprises first causing a reaction of a halogen-substituted alcohol with one of the following two substances: (a) a substituted piperidine in which a carbon-linked hydro on of piperidine has been replaced by an all: 1 group, and (b) a benzoylating agent; and subsequently causing a reaction of the other of such two substances with the result of the first reaction.

16. The process of producing substituted piperidino-alkyl nitro benzoates of the composition set forth in claim 1, which comprises first causing a reaction of a halogen-substituted alcohol with one of the following two 1,ve4,eos

substances: (a) a substituted piperidine in which a carbon-linked hydrogen of piperidine has been replaced by an alkyl roup, and (b) anitro benzoylchloride;and su sequently causing a reaction of the other of such two substances with the result of the first reaction. I

17. The process of producing substituted piperidino-alkyl nitro benzoates of the composition set forth in claim 1, which comprises first causing a reaction of a halogen-substituted alcohol with one of the following two substances: (a) a substituted piperidine in which a carbon-linked hydrogen of piperidine has been replaced by an alkyl group, and (b) a nitro benzoyl chloride; and subsequently causing a reaction of the other of such two substances with the result of the first reaction. and subsequently reducing the substituted piperidindalkyl nitro-benzoate to a substituted piperidino alkyl amino-benzoate.

18. The process of producing substituted piperidino-alkyl benzoates of the composition set forth in claim 1, which comprises causing a reaction of one of the following two substances: ((1) a substituted piperidine in which a carbon-linked hydrogen of piperidine has been replaced by an alkyl grou and (b) a benzoylating agent, with the resu t of the reaction of a halogen-substituted alcohol and the other of such substances.

19. The process of producing substituted piperidino-alkyl benzoates of the composition set Iorth in claim 1, which comprises causing a reaction of one of the following two substances: (a) a substituted piperidine in which a carbon-linked hydrogen of pipe?- idine has been replaced by an alkyl group, and (b) a nitro benzoyl chloride, with the result of the reaction of a halogen-substituted alcohol and the other of such substances.

20. The process of producing substituted piperidino-alkyl benzoates of the composition set forth in claim 1, which comprises causing a reaction of one of the following two substances: ((1) a substituted piperidine in which a carbon-linked hydrogen of piperidine has been replaced by an alkyl group, and (b) a nitro benzoyl chloride, with the result of the reaction of a halogen-substituted alcohol and the other of such substances, and subsequently reducing the substituted piperidino-alkyl nitro-benzoate to a substituted piperidino-alkyl amino-benzoate.

21. A piperidine derivative as expressed in claim 1, in which the g which is an aliphatic group is a methyl group.

22. A piperidine derivative as expressed in claim 1, in which the g which is an aliphatic group is a methyl group and in which R is a phenyl group.

23. A piperidine derivative as expressed in claim 1, in which the 1 which is an aliphatic group is a methyl grou and in which R is an amino-substituted p enyl group.

24. A piperidine derivative as expressed in claim 1, in which the 3 which is an ali hatic group is a methyl group and.in whic :0 15 three (3).

25. A iperidine derivative as expressed 1n claim 1, 1n which the 3 which is an aliphatic group is a methyl group and in which R is a phen 1 group an in which a? 1s three (3).

26. iperidine derivative as expressed n claim 1, in which the 1 which is an aliphat c group is a methyl group and in which R 1s an amino-substituted phenyl group and in which a: is three (3).

27. A piperidine derivat ve as expressed n claim 1, in which the y which 18 an aliphatic group is in the 2 position.

28' A I I c I claim 1, in which the 3 which 1s an ahphat c group is an alkyl group and is in the 2 position.

29. A piperidine derivative as expressed n claim 1, in which the 3 which is an aliphat c group is a methyl group and is In the 2 position.

30. A piperidine derivative as expressed claim 1, in which the 3 which 1s an aliphat c group is a meth l u and in which R is an unsubstitute p eny group.

31. A piperidine derivative as expressed in claim 1, in which the g which is an organic radicle is a methyl group and is in the 2 position and in which R is an unsubstituted phenyl group.

32. A piperidine derivative as expressed in claim 1, in which the which is an aliphatic group is in the 2 position and in which a: is three (3).

33. A iperidine derivative as expressed in claim 1, 1n whlircyli the y whish is anhaliphatlc on is anal groupan .isint e2posihim find in which a: is three (3). 34. A piperidine derivative as expressed in claim 1, in which the y which is an aliphatic group is a methyl group and is in the 2 position and in which a: is three (3).

35. A piperidine derivative including a substance of the general formula n-l-d-n ganic radicle containing an aliphatic group and in each of the four other places is a hydrogen atom.

36. A piperidine derivative as expremed in claim 35, in which in is a. plural integer.

37. A piperidine derivative as expressed in piperidine derivative as expressed in III claim 35, in which a: is a plural integer less than six (6).

38. A piperidine derivative as expressed in claim 35, in which a: is three (3).

39. A piperidine derivative as expressed in claim 35, in which the 3/ which is an organic radicle contains an aliphatic group of the parafiin series.

40. A piperidine derivative as expressed in claim 35, in which the y which is an organic radicle contains an alkyl group.

41. A piperidine derivative as expressed in claim 35, in which the g which is an organic radicle contains an alkyl group having less than four (4) carbon atoms.

42. A salt of a piperidine derivative of the formula set forth in claim 35, and an acid.

43. A piperidine derivative as expressed in claim 35, in which the 3 which is an organic radicle is a methyl group.

44. A piperidine derivative as expressed in claim 35, in which the 3/ which is an organic i'adicle is a methyl group and is in the 2 posiion.

In witness whereof I have hereunto set my hand at Indianapolis, Indiana, this 29th day of March, A. D. one thousand nine hundred and twenty seven.

SAMUEL M. MGELVAIN.

6 messes claim 35, in which a: is a plural integer less than six (6).

38. A piperidine derivative as expressed in claim 35, in which a: is three (3).

39. A piperidine derivative as expressed in claim 35, in which the g which is an or anic radicle contains an aliphatic group 0 the paraflin series.

40. A piperidine derivative as expressed in claim 35, in which the 3 which is an organic radicle contains an alkyl group.

41. A piperidine derivative as expressed in claim 35, in which the 3 which is an organic radicle contains an alkyl group having less than four 4) carbon atoms.

42. A sa t of a piperidine derivative of the formula set forth in claim 35, and an acid.

43. A piperidine derivative as expressed 1 n claim 35, in which the 3/ which is an organic radicle is a methyl group.

44. A piperidine derivative as expressed 1n claim 35, in which the y which is an organic radicle is a methyl group and is in the 2 position.

In witness whereof I have hereunto set my hand at Indianapolis, Indiana, this 29th day of March, A. D. one thousand nine hundred and twenty seven.

SAMUEL M. McELVAIN.

CERTIFICATE OF CORRECTION.

Patent No. 1, 784,903.

Granted December 16, 1930, to

SAMUEL M. McELVAIN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 15, for-the word "bases" read basis; page 3. line 129, for "groups" read group; page 4, line 23, strike out the word "compounds", and line 103, claim 10, before the word "group" insert the word phenyl; and that the said Letters Patent should be read with these corrections theieiiPtiut the same may conform to the record of the case in the Patent Office.

Signed and sealed this 20m day of January, A. o. 1931.

(Seal) M. J. Moore, Acting Comisaioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 1,784,903. Granted December 16, 1930, to

SAMUEL M. McFLVAIN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 15, for'the word "bases" read basis; page 3, line 129, for "groups" read group; page 4, line 23. strike out the word "compounds", and line 103, claim 10, before the word "group" insert the word phenyl; and that the said Letters Patent should be read with these corrections theim the same may conform to the record of the case in the Patent Office.

Signed and sealed this 20th day of Janua y. A. D. 1931.

M. J. Moore, Acting Commissioner of Patents. 

